The present invention relates to a thermally developable light-sensitive material capable of forming a dye image by a thermal dry process. In particular, the present invention relates to a thermally developable light-sensitive material capable of forming a color image by diffusion transfer of a dye.
Thermally developable light-sensitive materials which provide image in a simple and quick way through development that is conducted by a thermal dry process have been known and these materials as well as methods for forming image thereon are described in many references such as "Shashin Kogaku no Kiso (Fundamentals of Photographic Engineering), pp. 553-555, Corona-sha, 1979, and Research Disclosure (RD-17029), pp. 9-15, June, 1978.
Active efforts have recently been made to design thermally developable color light-sensitive materials which produce color image using a variety of dye-providing materials. Among the processes proposed so far, one that produce color image by transferring the diffusible dye that has been released or formed as a result of thermal development is reputed for the many advantages it offers such as image stability and sharpness, as well as simplicity and rapidity of processing. Thermally developable color light-sensitive materials employing this transfer process and methods for forming image by this process are described in the specifications of many patents such as Japanese Patent Application (OPI) Nos. 12431/1984 (the term OPI as used hereinafter means an unexamined published Japanese patent application), 159159/1984, 181345/1984, 229556/1984, 2950/1985, 1986, 61158/1986, 61157/1986, 180550/1984, 132952/1986, 139842/1986, and U.S. Pat. Nos. 4,595,652, 4,590,154 and 4,584,267.
In the thermally developable light-sensitive materials of the type described above, dye-providing materials often diffuse together with the formed or released dye when the latter is subjected to heat diffusion transfer and the diffusing dye-providing materials will subsequently form or release a dye in layers where such a phenomenon should not occur. This can cause color mixing, which is detrimental to the color purity of image and becomes severe when a hot solvent is incorporated in the light-sensitive material with a view to activating thermal development and dye transfer. Similar color mixing can take place when a dye-providing material of the non-transfer type is employed.
In order to prevent this undesirable color mixing, studies have been conducted that are directed to improving the immobility of dye-providing materials. The accomplishments of these studies have been described in the specifications of many patents such as Japanese patent application (OPI) Nos. 159159/1984, 181345/1984, 2950/1985, 57943/1986, 59336/1986, 61157/1986, 61158/1986, 65037/1987, 44738/1987, 129852/1987 and 143049/1987. Polymeric dye-providing materials have particularly high immobility and are preferably used to prevent color mixing. However, the use of such polymeric dye-providing materials has not been a complete solution to the problem of color mixing in cases where a smaller amount of binder or an increased amount of thermal solvent is used with a view to improving developability or transferrability.